HO from outer zone to inner zone can fail because :
– your settings are wrong (what are your settings ?)
– the inner zone is “congested” (ho failure due to congestion)
– cross sector : the inner zone is actually located in another sector 🙂
– hardware problems : the Rx or Tx path in the BTS is faulty on the inner zone TRX.
UL:underlaid(outer zone) and OL:overlaid(inner zone). We are using 900 in UL and 1800 in OL. Major cause of UL to OL failure is the coverage gap between two. The handover boundary can be fine tuned to resolve this problem.
if you are unsure the swith, you may use a software to have a test of it to make sure what the problem is. i recommend a software(CELLTEST) which is easy to use and has good performence.
we have software base on PC & PDA both. so you can use PDA to test the hotspot place like train station and sport ground, and PC version for drive test or other usage.